Dwyfam and Dwyfach, who saved themselves in a vessel without rigging,
and it was by them that the island of Prydian was repeopled."

Pictet here observes:

"Although the triads in their actual form hardly date farther than the
thirteenth or fourteenth century, some of them are undoubtedly connected
with very ancient traditions, and nothing here points to a borrowing
from Genesis.

"But it is not so, perhaps, with another triad, speaking of the vessel
Nefyddnaf-Neifion, which at the time of the overflow of Llyon-llion,
bore a pair of all living creatures, and rather too much resembles the
ark of Noah. The very name of the patriarch may have suggested this
triple epithet, obscure as to its meaning, but evidently formed on the
principle of Cymric alliteration. In the same triad we have the
enigmatic story of the horned oxen (ychain banog) of Hu the mighty, who
drew out of Llyon-llion the avanc (beaver or crocodile?), in order that
the lake should not overflow. The meaning of these enigmas could only be
hoped from deciphering the chaos of barbaric monuments of the Welsh
middle age; but meanwhile we cannot doubt that the Cymri possessed an
indigenous tradition of the Deluge."

We also find a vestige of the same tradition in the Scandinavian Ealda.
Here the story is combined with a cosmogonic myth. The three sons of
Borr--Othin, Wili, and We--grandsons of Buri, the first man, slay Ymir,
the father of the Hrimthursar, or ice giants, and his body serves them
for the construction of the world. Blood flows from his wounds in such
abundance that all the race of giants is drowned in it except Bergelmir,
who saves himself, with his wife, in a boat, and reproduces the race.